Grinding machine



April 12, 1960 s. M. TROTTIER GRINDING MACHINE Filed March 31, l959 INVENTOR GEEA ED M. 7POT77EE A T'TOENE'Y Sta Paten The invention relates to grinding machines and more particularly to a grinding wheel, feeding-mechanism.

One object of the invention is to provide a simple and thoroughly practical feeding mechanism for a cylindrical grinding machine. Another object of the invention isto 7 provide a feeding mechanism whereby an ultra-fine feed may be obtained to, facilitate precisely sizing 'a work- 12 9.0 feeding mechanism whereby the grinding wheel may be moved first at a rapid positioning rate, then at a slower grinding feed and finally at. an ultra fine feed during the preeising operation. Other objects will be in part obvious ,or in part pointed out hereinafter.

The invention accordingly consists in the features of construction, combinations of elements, and arrangements of parts, as will be exemplified in the structure to be hereinafter described, and the scope of the application of which will be indicated in the following claims.

. One embodiment ,of the invention has been illustrated in the drawing which is a combined cross-sectional view of a grinding wheel feeding mechanism together with the hydraulic and electrical control circuits therefor.

Animproved hydraulically operated grinding machine has been illustrated in the drawings comprising a base 10 which serves as a support for a longitudinally reciprocable work table 11. The work table 11 isslidably mounted on a flat way 12 and a V-way 13 formed on the upper surface of the base 10.

A transversely movable grinding wheel slide 15 is slidably mounted in the usual manner on a V-way .1-4 and a flat, way (not shown) formed on the upper surface of the base 10. The wheel slide 15 serves as a support for a rotatable grinding wheel 16 which is mounted on one end of a rotatable wheel spindle 17. The wheel spindle 17 is driven by an electric motor 18 mounted on the upper surface of the wheel slide 15. The motor 18 is provided with a motor shaft 19 having a V-groove. pulley 20 mounted thereon. The pulley 20 is connected by V-belts 21 with a V-groove pulley 22 mounted on the other end of the wheel spindle 17. a

The wheel slide 15 is arranged to be fed transversely relative to the base 10 by means of a feed screw 25 which is journaled at its right hand end in anti-friction bearings (not shown) carried by a slidably mounted sleeve 26. The sleeve 26 is arranged to slide within a cylindrical aperture 27 formed in the base 10. A reduced cylindrical portion 28 onthe left hand end of the feed screw 25 is slidably connected within a rotatable sleeve 29. The sleeve 29 is journaled in anti-friction bearings 30 carried by the base 10. The wheel slide 15 is provided with a depending bracket 31 which supports a half nut 32 meshing with the feed screw 25.

It will be readily apparent from the foregoing disclosure thata rotary motion of the feed screw 25 will be 2 Another object is to provide a grinding wheel Patented Apr. 12, 1960 imparting a rapid approaching and receding movement to the wheel slide 15 comprising a cylinder 35 which is arranged in axial alignment with the feed screw 25. The cylinder 35 contains a slidably mounted piston 36 which ismounted on the right hand end of a piston rod 37.

The left hand end of the piston rod 37 is connected to imparted through the feed nut 32 to move the wheel slide 15 1 together with the either. direction.

A hydraulically operated mechanism is provided for grinding wheel 16 transversely in the slidably mounted sleeve 26.

' A piston-type control valve 38 is provided for controlling the admission to and exhaust of fluid under pressure from the cylinder 35. The control valve 38 comprises a valve stem 39 having a plurality of spaced valve pistons formed integrally therewith to form a pair of spaced valve chambers 40 and 41. A compression spring 42 serves normally to hold the valve stem 39 in a right hand end position.

When fluid under pressure is passed through a pipe 43 into the valve chamber 40,

it passes through a pipe or passage 44, through a port 45 into a cylinder chamber to' move the piston 36 together with the feed screw 25 and the-wheel slide 15 toward the right. Fluid under pressure passing through the passage 44 may also pass through both a ball check valve 46 and a throttle valve 47, through a pipe or passage 48, through a port 49 into the cylinder chamber 50. During movement of the piston 36 toward the'right, fluid within a cylinder chamber 51 exhausts through a passage 52, through the valve chamber 41 and through an exhaust pipe 53.

A fluid pressure system is provided for supplying fluid under-pressure to the pipe 43 comprising a motor driven fluid pump 55 which draws fluid through a pipe 56 from a reservoir 57 and passes fluid under the desired pressure through the pipe 43. A pressure relief valve 58 is connected to the pipe 43 to facilitate by-passing excess fluid under pressure directly to the reservoir 57 so as to maintain a substantially uniform operating pressure within the system.

An electrical system including leads L1 and L2 is provided fo'r'energizing the various electrical elements of this device such as the motors 18 and 110 and the solenoid S1 through the various switches and the timer mechanism as shown in the drawing.

The rearward movement of the piston 36 may be cushioned by ,a dash pot piston 60 as it approaches the right hand end of its movement. The movement of the dash pot piston 60 toward the right exhausts fluid from adash pot chamber'61 through a throttle valve 62, through a pipe 63 into the valve chamber 41 and thereafter exhausts into-the reservoir -57. It will be readily apparent from the foregoing disclosure that by manipulation of the throttle valve 62, the rate of cushioning the movement of the piston 36 may be regulated as desired.

enters the valve chamber 41 and passes through the passage 52 ,-'into the cylinder chamber 51 to start the movement of .the piston, 36 together with the feed screw 25,

the wheel slide 15 and thegrinding wheel 16 toward the left; At the same time fluid under pressure passes from the valve chamber 41 "through the pipe 63, through a ball check valve 64 into the dash pot chamber 61 so as to reset the dash pot piston 60 in its initial position, that is, its left hand end position.

The piston 36 moves toward the left at a rapid rate controlled by fluid exhausting from the cylinder chamber 50 through'the port '45 and 'the passage 44'and also through the port 49, through the throttle 40 and thereafter exhausts through the pipe 53 into the reservoir 57. Movement of the piston 36 at a rapid through the pipe or passage 48, valve 47 into the valve chamber y '7 n ,932,1 K v 7 rate continues until the piston 36 covers the port 45 so that further exhaust of fluid from the cylinder chamber 50 must pass through the throttle valve 47 which cushions the forward approaching movement of the grinding wheel before the piston 36 engages the left hand end of the cylinder 35.

A suitable feeding mechanism is provided for producing a slowprecise feeding movement of the grinding wheel during the grinding operation. In the prefered form, a hydraulically operated mechanism is provided so that the feed screw 25 may be rotated either continuously for a plunge-cut grinding operation or intermittently at the ends of the table stroke for a traverse grinding operation. A manually operable feeding wheel 70 mounted on a shaft 71 carries a gear 72 which meshes with a gear 73 on a rotatable shaft 74. The right hand end of the shaft 74 is slidably connected within the rotatable sleeve 29. The feed wheel 70 is provided with the usual and well known micrometer feed adjusting mechanism 75 which serves to facilitate adjusting a stop abutment 76 relative to a stop surface 77 formed on the upper end of a feed pawl 78. The feed pawl 78 is pivotally supported by a stud 79 which is mounted on the front of the machine base. It will be readily apparent from the foregoing disclosure that by manipulation of the feed wheel 70, the feed screw 25 may be rotated in either direction to cause a forward or rearward movement of the wheel slide and the grinding wheel 16. The direction of rotation of the feed wheel 70 determines the direction of movement of the wheel slide 15 and the grinding wheel 16.

A hydraulically operated mechanism is provided to facilitate imparting a rotary motion of the feed screw 25 to produce the desired grinding feed of the wheel '16. This mechanism comprises a cylinder 85 which con tains a slidably mounted piston 86. The upper surface of the piston 86 is provided with rack teeth 87 which mesh with a gear 88. The gear 88 is mounted on a rotatable shaft 89 which also supports a gear 90 meshing with the gear 73. It will be readily apparent from the foregoing disclosure that when the piston 86 is moved within the cylinder 85, a rotary motion will be imparted through the gears 88, 90 and 73 to impart a corresponding rotary motion to the feed screw 25. When fluid under pressure is passed through a pipe 91 into a cylinder chamber 92 formed at the left hand end of the cylinder 85, the piston 86 will be moved toward the right so as to impart a rotary motion through the gear mechanism above described to rotate the feed screw 25 clockwise and the feed wheel 70 in a counter clockwise direction so as to cause a forward grinding feed to the wheel 16. During this movement fluid within a cylinde chamber 93 exhausts-through a-pipe 94. a

A shuttle type control valve 100' is provided for controlling the admission to and exhaust of fluid fr'omthecylinder 85. This valve comprises a slidably mounted valve 101 having a; plurality of valve pistons formed in-- tegrally therewith to form a plurality of spaced valve chambers'102and 103'. 7

The valve 100 is preferably actuated by and in: timed relation with the feed control valve38. A pipe 104' is connected between the pipe 44 and an end chamber chamber 105 formed at the right hand end of the valve 100. Similarly the pipe 63 is connected to an end'cha'mher 106 formed at the left hand end of the valve100."

In the position of the-valve 100" shown in the drawings fluid under pressure in the pipe 43 passes into the valve chamber'103, through the pipe 94 into the cylinder chamber 93 to move the piston 86 toward the leftthereby movingl'the wheel slide 15 and the-grinding wheel 16' to a rearward: or inoperative position, that is, toward the right. as shown in the drawing. Fluid" under pressure within the chamber 93- holds the parts in this position until. a feeding cycle is initiated Wheathe: solenoid S1' is energized to initiatc a forward approaching movement of the wheel slide 15 and the grinding wheel 16, fluid under pressure passing through the passage 52, passes through the pipe 63 into the valve chamber 106 so as to shift the valve member 101 toward the right into a right hand end position. In this position, fluid under pressure from the pipe 43 enters the valve chamber 102 and passes through the pipe 91 into the cylinder chamber 92 to start the piston 86 moving toward the right thereby imparting a forward feeding movement by means of the feed screw 25 to the grinding wheel slide 15 and the grinding wheel 16. During forward feeding movement fluid within the cylinder chamber 93 exhausts through the pipe 94, into the valve chamber 103 and exhausts through a pipe 107. During the forward feeding movement, the feed wheel moves in a counter clockwise direction and continues until the stop abutment 76 engages the stop surface 77 thereby terminating the forward feeding movement of the grinding wheel 16.

A motor 110 is provided for imparting a rotary motion to thework piece 111 to be ground. This motor is operatively connected to a relay switch 112. It is desirable to start the motor 110 to impart a rotary motion to the work piece 111 when a forward feeding movement of the grinding wheel 16 is initiated. This is preferably accomplished by a piston type control valve 115 comprising a slidably mounted valve stem 116 and a valve piston 117. The valve stem'116 is normally held in a right hand end position by compression spring 118. The valve stem 116 is arranged to actuate a normally open limit switch 119 when the valve piston 117 is moved toward the left. A pipe 120 is connected between the pipe 63 and the valve 115 so that when fluid under pressure is passed through the pipe 63 into a valve chamber .121, the piston 117 will be moved toward the left to close the limit switch 119 thereby closing a circuit to energize the relay switch 112 to start the work driving motor 110. V

A piston type control valve is provided to control the rate of exhaust of fluid from the cylinder 85 so that during the initial grinding operation the grinding wheel may be advanced at a desired grinding rate and at a predetermined point in the grinding operation the rate of in'fe'ed may be reduced to an ultra-fine feed which may be regulated as desired. The valve 130 is apiston type valve comprising a valve stem 131 having a plurality of spacedvalve pistons which form a plurality of spaced valve chambers 132, 133, 134, 135,- and 136.

A compression spring 137 serves normally to hold the 140 which is arrange'd in the path of the valve stem 1-31'.

A cam 141 adjacent to the stop abutment 76 on the feedwheel 70 is arranged to engage a cam face 142 on the feed pawl 78 during a counter clockwise rotary motion of the feedwheel 70 to rock the feed pawl 78 and the arm 139' in a counter clockwise direction thereby shifting. the valve stem 131 toward the right. 7

At the start of the infeeding movement, the valve member 101' shifts toward the right so that flui'd' exhaus'tingfrom' the cylinder chamber 93 through the pipe 94 enters the va'lve charn'ber 103 and passes through a pipe 107, througha needle valve 146, through a needle valve 147, through a pipe 148 and through a pipe 149 into the reservoir 57. At the same time fluid under pressure' passing through the pipe 107 passes through a pipe into the valve chamber 133', through a central-passage" 138into the valve chamber 132 andexhausts through the pipe 149 irito the reservoir 57. It will be readily apparent from the foregoing disclosure that" the a valve piston on valve stem 131 initial grinding feed will be controlled by the needle valve 146.

As the grinding operation proceeds, shortly before the Work has been ground to a predetermined size the cam 141 moving in a counter clockwise direction swings the pawl arm 78 and the arm 92 in a clockwise direction to'move the valve stem 131 toward the right so that closes the port at the end of the pipe 145. After this port has been closed fluid must exhaust from the needle valve 146 through the fine feed needle valve 147, through the pipe 148 and the pipe 149 into the reservoir 57. It will be readily apparentfrom the above disclosure that by manipulation of the needle valves 146 and 147, the rate of the initial feed and also the rate of the ultra-fine feed may be readilycontrolled as desired.

The machine may be equipped with a steady rest 150 which as illustrated is identical with that disclosed in the prior US. patent to Oiva' E. Hill, No. 2,844,921, dated July 29, 1958, to which reference may be had for details of disclosure not contained herein. The steady rest 150 comprises work steadying elements illustrated as a pair of pivotally mounted work steadying shoes 151 and 152 which are actuated by a hydraulically operated mechanism comprising a cylinder 153 which contains a slidably mounted piston 154. In the position of the parts as shown in the drawing, fluid under pressure from the pipe 43 enters the valve chamber 135 in the valve 130 and passes through a pipe 155 into a cylinder chamber 156 to hold the piston 153 in a left hand end position with the work steadying shoes 151 and 152 out of engagement with the work piece 111. During movement of the piston 154 into a left hand end position fluid within the cylinder chamber at the left hand end of the cylinder 153 exhausts through a pipe 157, into a valve chamber 136 and through the pipe 149 into the reservoir.

When the valve stem 131 moves toward the right, fluid entering the valve chamber 135 passes through the pipe 157 to move the piston 154 toward the right thereby swinging the work steadying shoes 151 and 152 into operative supporting engagement with the work piece 111 being ground. I

When the valve stem 131 is moved toward the right to initiate an ultra-fine feed, fluid is also passed from the pipe 43, through the valve chamber 135, and thence through the pipe-157 into the left hand end of the cylinder156, Fluid exhausts from the right hand end of the cylinder 156 through a throttle valve 170 which controls the normal rate of movement of the work steadying shoes into operative engagement with the work piece.

When fluid is passed from valve 130 through pipe 157 to move piston I54 toward the right, fluid is exhausted from the right hand end of the cylinder 153 through the throttle valve 170 which controls the normal movement of the shoes. Fluid is also metered through a shuttle type metering valve 160 to facilitate a rapid movement of the steadyrest shoes 151 and 152 into an operative position adjacent to the periphery of the work piecelllk The valve 160 comprises a slidably mounted valve member 161 displaced to the right by fluid from pipe.157, and having a pair of spaced valve pistons formed integrally therewith to form a valve chamber 162. A throttle valve 164 is provided to control the rate of movement of the valve member 161 toward the right. During movement of the valve member 161 toward the right fluid exhausting from the cylinder chamber 153, through'the pipe 155 passes through a pipe 169, and during movement of the valve member 161 toward the right fluid may 'pass through the valve chamber 162 and through a pipe 168 into the exhaust pipe 149 thereby- 'perrnitting a rapid movement of the work steadying shoes 1551 and 152 toward an operative position. When the" valve member 161 reaches the right hand end of valve 160, pipe 169 isagain closed so that final movement of the shoes is at the normal rate controlled by throttle valve 170.

The ball check valve 167 is provided to bypass fluid around the throttle valve 164 when fluid is reversed to rapidly'return the valve member 161 into a left hand end position. Similarly a ball check valve 171 is provided to bypass the throttle valve 170 when fluid under pressure is passed through the pipe 155 into the cylinder 156 to facilitate a rapid movement of the piston 154 toward the left to rapidly move the shoes 151 and 152 to an inoperative position.

In order to facilitate controlling the normal and ultrafine feed and also to control the steadyrest shoes, a plurality of independently operable control means comprising valves 175, 176, and 177 are provided. If a normal and ultra-fine feed together with operation of the steadyrest is desired, the valves 175 and 176 are opened and the valve 177 closed. If a normal and ultra-fine feed are desired without the use of the steadyrest, valves 175 and 177 are closed and 176 opened. If only a normal feed together with operation .of the steadyrest is desired, the valves 175 and 177 are opened and the valve 176 closed; If an ultra-fine feed is desired together with operation of the steadyrest, the valve 175 is opened and the valves 176 and 177 closed. If a normal feed only is desired without operation of the steadyrest, valves 175 and 176 are closed and 177 opened. If an ultrafine feed only is desired without operation of the steadyrest, the valves 175, 176, and 177 are all closed. If it is desired to render the valve inoperative, independently operable control means comprising the stop screw may be backed off and if all the valves 175,176, and 177 are opened a normal feed is obtained. If the valves and 176 are opened and valve 177 is closed still with valve 130 inoperative, a normal feed is obtained as above. In both of the latter cases the Steadyrest is maintained inoperative.

The feeding cycle may be controlled automatically by means of the old and well known electric contact gage or may be controlled by an electric timer. As illustrated in the drawing, a timer T1 is provided for controlling the grinding cycle. The timer T1 may be any of the well known electric timers, such as, for example, the Microflex automatic reset timer manufactured by the Signal Corporation of Molene, Illinois. A manually operable control lever 180 is pivotally mounted on the front of'the-machine base. in a counter clockwise is closed to energize the gize the solenoid S1 thereby shifting the valve 38 toward the left to start a feeding cycle. A main switch 182 is closed to energize the electrical system and to render the circuit for motor 110 operative to limit switch 119. A switch SW2 is closed to start the grinding wheel driving motor 18. V

As above described the operation of the improved feeding mechanism will be readily apparent from the foregoing disclosure. When the timer T1 is energized to energize the solenoid S1, the valve 38 is shifted toward the left to start the piston 36 together with the wheel slide 15 and the grinding wheel 16 moving rapidly toward the left to position the periphery of the grinding wheel in operative relationship with the work piece 111 to be ground. The fluid under pressure passes through the pipe 63 to shift the valve member 101 toward the right so that fluid under pressure from the pressure pipe 43 passes through the pipe 91 to start the piston 86 moving in av direction toward the right thereby rotating the feed screw 25, as above described to advance the wheel 16 at a normal grinding rate. This movement continues until rotation of the feed wheel in a counter clockwise direction causes the cam 141 to engage the cam face 142 on the feed pawl 78 to rock the feed pawl 78 together with the downwardly extending arm 139 in a counter clockwise direction so as to shift thevalve stem When the lever .180 is rocked; direction a starter switch 181 timer T1 which serves to ener- .131 toward the right. This movementof the valve stem 131 shifts the valve so that fluid passing through the pipe it)? must exhaust through both the needle valves -146 and 147 to reduce the grinding feed to a very slow ultrafine feed. This feeding movement at an ultra-fine feeding rate continues until the timer T1 times out thereby deenergizing the solenoid S1 to release the compression of the spring 42 thereby returning the valve stem 39 into a righthand end position, as shown in the drawing. In this position of the valve stem 39, fluid under pressure is passed into the valve chamber 40, through both the ports 45 and the port 49 to move the piston 36 toward the right so as to move the wheel slide and the grinding wheel 16 toward the right to an inoperative position. At the same time fluid under pressure is passed through the pipe 94 to move the piston 86 toward the left thereby resetting the parts for the next feeding cycle. M It will thus be seen that there has been provided by this invention apparatus in which the various objects hereinabove set forth together with many thoroughly practical advantages are successfully achieved. As many possible embodiments may be made of the above invention and as many changes might be made in the embodiment above set forth, it is to be understood that all matter hereinbefore set forth or shown in the accompanying drawing is to be interpreted as illustrative and not in a limiting sense.

I claim: i 1. A wheel feeding mechanism for a grinding machine having a transversely movable rotatable grinding wheel, means including a nut and screw mechanism to feed said wheel in either direction, means including a piston and cylinder operatively connected to move said screw axially rapidly to positionthe grindingwheel for a grinding operation, movable steadyrest means for supporting a'work, piece, means including a second piston and cylinder oper-- atively connected to actuate said nut and screw, means tocontrol the exhaust offluid from the latter cylinder to produce a predetermined normal grinding feed, and means thereafter to slow down the rate of infeed at a predetermined point in the grinding cycle to reduce the normal infeeding movement to an ultra-fine feed before the final size is reached and to actuate said steadyrest means at a predetermined point in the grinding cycle.

2. A wheel feeding mechanism for a grinding machine having a transversely movable rotatable grinding Wheel, means including a nut and screw mechanism to feed said wheel in either direction, means including a piston and cylinder operatively connected to move said screw axially rapidly to position the grinding wheel for a grinding operation, movable steadyrest means for supporting a work piece, means including a second piston and cylinder operatively connected to actuate said'nut and screw, a throttle valve to control the exhaust of fluid from said latter cylinder to produce a predetermined normal grinding feed, a second throttle valve which is rendered operative at a predetermined point in the grinding cycle to reduce the infeeding movement to an ultra-fine feed before final size is reached and control means for rendering said second throttle valve operative and for concurrently actuating said steadyrest.

3. A grinding wheel feeding mechanism for a grinding machine having transversely movable rotatable grinding wheel, means including a nut and screw mechanism to feed said wheel in either direction, a manually operable feed wheel operatively connected to actuate said nut and screw mechanism, a positive stop to limit the rotary motion of said feed wheel, means including a piston and cylinder operatively connected to impart a rotary motion to the fed screw and the feed wheel, a throttle valve to control the exhaust of fluid from said cylinder to produce a normal grinding feed, a second throttle valve operatively connected to control the exhaust of fluid from said cylinderto produce an ultra-fine feed, mechanical actuator means, and a control valve actuated by said meqhanical actuator means in timed relation with the rotary motion of the feed wheel to render the first throttle valve ineffective before the work piece has been ground to a predetermined size so as to reduce the infeeding movement to an ultra-fine feed. 7

4. A grinding wheel feeding mechanism for a grinding machine having a transversely movable rotatable grinding wheel, means including a nut and screw mechanism to feed said wheel in either direction, a manually operable feed wheel operatively connected to actuate said nut and screw mechanism, a positive stop to limit the rotary motion of said feed wheel, means including a piston and cylinder operatively connected to impart a rotary motion to the feed screw and the feed wheel, a throttle valve to control the exhaust of fluid from said cylinder to produce a normal grinding feed, a second throttle valve operatively connected to control the exhaust of fluid from said cylinder to produce an ultra-fine feed, a work steadying rest having a pair of work steadying shoes, means including a piston and cylinder operatively connected to move said shoes into and away from operative engagement with a work piece being ground, and a control valve actuated by and in timed relation with the rotary motion of the feed screw to pass fluid under pressure to the steadyrest cylinder to move the steadyrest shoes into operative engagement with the work piece and to render the first throttle valve ineffective before the work piece has been ground to a predetermined size so as to reduce the infeeding movement of the grinding wheel to an ultra-fine feed.

5. In a grinding machine as claimed in claim ,4, the combination with the parts and features therein specified of an electric timer operatively connected to control the duration of the grinding cycle.

6. In a grinding machine having a transversely movable rotatable grinding wheel, means including a nut and screw mechanism to feed said wheel transversely in either direction, means including a piston and cylinder operatively connected to impart a rapid axial movement to the feed screw to move the grinding wheel to and from an operative position, a manually operable feed wheel operatively connected to actuate said nut and screw mechanism, a positive stop mechanism to limit the rotary motion of the feed wheel to terminate the grinding operation, a second piston and cylinder operatively connected to impart a rotary motion to the feed screw and the feed wheel, a throttle valve to control the exhaust of fluid from said latter cylinder to produce a normal grinding feed, a second throttle valve operatively connected to control the exhaust of fluid from said cylinder to produce an ultrafine feed, a steadyrest means movable into and out of engagement with a work piece, and a feed and steadyrest control valve actuated by and in timed relation with the rotary motion of the feed wheel to render the first throttle valve ineffective before the work ground to a predetermined size so as to reduce the rate of infeed to an ultra-fine feed and to initiate movement of said steadyrest means into engagement with a work piece. V

7. A grinding machine, as claimed in claim 6, and the combination with the parts and features therein specified of a pair of control valves, and operative connections between said control valves and the feed and steadyrest control valve to render said latter valve inoperative when desired. I

8. In a grinding machine having a transversely movable rotatable grinding wheel, a rotatable work support, a work steadyrest including retractable work steadying elements, a steadyrest, a piston and cylinderto actuate said elements, a wheel feed mechanism including a feed piston and cylinder to feed said wheel in either direction, means including a feed wheel to actuate said wheel feed mechanism, a control valve to control the exhaust of fluid from the feed cylinder and to control the admiss on to and exhaust of fluid from the steadyrest cylinder, means piece has been 1 actuated by and in timed relation with said feed wheel to actuate said valve 50' as to reduce the rate of infeed of the wheel feed mechanism to an ultra-fine feed and to move said work steadying elements into operative engagement with the Work at a predetermined time in the 5 grinding cycle and a plurality of independently operable control means to selectively activate and deactivate the portions of said control valve for controlling said feed mechanism and said 'steadyrest.

References Cited in the file of this patent UNITED STATES PATENTS 2,599,992 Hill June 10, 1952 2,639,563 Swainey May 26, 1953 2,844,921 Hill July 29, 1958 

